CMV is a major cause of death for patients with AIDS. CMV pneumonia is often found at autopsy, but it is rarely found antemortem for reasons that are not understood. As antipneumocystis prophylaxis is used more commonly, it is likely that CMV will become an increasingly important cause of morbidity and mortality. Effective anti-CMV drugs are now available. It is thus important to learn how to diagnose this entity invasively and non-invasively. This study will assess sputum, bronchoalveolar lavage and transbronchial biopsy by a variety of conventional and novel approaches to CMV. Patients will be followed, but these data will not be used to determine therapy since their relevance is currently unknown. The importance of this study is that it is a comprehensive effort to determine how CMV pneumonia can be diagnosed antemortem: CMV is a major cause of death in AIDS patients.